Black market was totally stable in the 1000:1 mark for months, until the actions from the gov to stop the presidential referendum made again the rich unhappy and they decided to attack with all they have and this includes the media.
95% of the imports in Venezuela are made using the official rates and thats a bit complicated to explain, there is 2 rates wich are 1usd:13bsf (a price fully subsided used mostly for food and items that are considered "basic") and 1usd:658 for everything else and then there was the black market dollar wich is now 1usd:1758bsf
The thing is you can sit here and say the dolar is 1:2000 but it doesn't really mean thats the cost, thats where everyone fails, because neither the venezuelans have the money to pay for it or people want our currency, there is an special case of people doing this kind of trades and are the ones that are fleing the country, emigrating to other places and are desperated in need of USD
In the other hand, is somehow totally fake that we are paying this prices, in fact, noone imports anymore since gov barely gives USD at subsided price thus this is why we are now under scarcity problems.... so there you go.. offer and demand sets the prices but theres actually not really demand, I mean there is an insane demand but not demand for the 2000:1 price, thats just a political fight.